Asked by BJ
Desiree invested some money at 9% and $100 less than three times the amount at 7%. Her total annual interest was $83. How much did she invest at each rate?
Answers
Answered by
Bosnian
9 % = 9 / 100 = 0.09
7 % = 7 / 100 =0.07
x = the amount of money
$100 less then three times the amount = 3 x - 100
x * 0.09 + ( 3 x - 100 ) * 0.07 = 83
0.09 x + 3 x * 0.07 - 100 * 0.07 = 83
0.09 x + 0.21 x - 7 = 83
0.3 x - 7 = 83
0.3 x = 83 + 7
0.3 x = 90
x = 90 / 0.3
x = 300
3 x - 100 = 3 * 300 - 100 = 900 - 100 = 800
$300 with interest 9% and $800 with interest 7%
$300 * 0.09 + $800 * 0.07 = $27 + $56 = $83
7 % = 7 / 100 =0.07
x = the amount of money
$100 less then three times the amount = 3 x - 100
x * 0.09 + ( 3 x - 100 ) * 0.07 = 83
0.09 x + 3 x * 0.07 - 100 * 0.07 = 83
0.09 x + 0.21 x - 7 = 83
0.3 x - 7 = 83
0.3 x = 83 + 7
0.3 x = 90
x = 90 / 0.3
x = 300
3 x - 100 = 3 * 300 - 100 = 900 - 100 = 800
$300 with interest 9% and $800 with interest 7%
$300 * 0.09 + $800 * 0.07 = $27 + $56 = $83
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